Chao Yu

Sun Yat-sen University

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Xiaoxia Yang

Kunming University of Science and Technology

Bin Huang

Kunming University of Science and Technology

Junping Chen

Shanghai Astronomical Observatory

Butera Hassan

Kunming University of Science and Technology

Yize Zhang

First Affiliated Hospital of Zhengzhou University

Changkai Wang

Xi'an Polytechnic University

Xuejun Pan

Kunming University of Science and Technology

Jianhe Zhang

Fujian Provincial Hospital

Yuyu Zhou

University of Hong Kong

Lun Zhang

University College London

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Chinese Academy of Sciences

Kunming University of Science and Technology

Nanjing University

Peking University

Zhejiang University

China Meteorological Administration

University of Chinese Academy of Sciences

Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application

Shanghai Astronomical Observatory

Jiangxi University of Science and Technology

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Improving BDS broadcast ephemeris accuracy using ground-satellite-link observations

Satellite Navigation (2022)

Junping Chen Jungang Wang Chao Yu Yize Zhang Bin Wang

Abstract The BeiDou Navigation Satellite System (BDS) employs a hybrid constellation including GEO (Geosynchronous Earth Orbit), IGSO (Inclined Geosynchronous Orbit), and MEO (Medium Earth Orbit) satellites, where the GEO and IGSO satellites are critical to providing continuous and reliable Positioning, Navigation, and Timing (PNT) services in the Asia–Pacific region. To handle the inconsistency between the satellite orbits and clocks in the broadcast ephemeris, which are determined by the Orbit Determination and Time Synchronization (ODTS) and the Two-way Satellite Time Frequency Transfer (TWSTFT) technique, respectively, we present the strategies using ground-satellite-link observations to improve the accuracy of broadcast ephemeris. The clock differences between the ODTS and TWSTFT techniques are used for correcting the radial orbit component to derive the refined orbits, which are used to generate the refined broadcast ephemeris. The test results show the precision of the refined orbits is improved by 50–60% in the 3-h to 12-h predicted arcs for the GEO satellites, and by 40–50% for the IGSO satellites. Moreover, the validation using satellite laser ranging observations shows the mean precision of the refined broadcast ephemeris is improved by 27% compared to the original one. Applying the proposed strategies in the BDS Operational Control Segment (OCS), the time evolution of BDS Single Point Positioning (SPP) in the period from Jan. 2016 to April 2021 is evaluated. The SPP accuracy is improved from 1.94, 2.06 and 3.29 m to 1.39, 1.85, and 2.39 m in the north, east, and up components, respectively. Further update with the inclusion of BDS-3 satellites improve the corresponding SPP precision to 0.68, 0.70 and 1.91 m.

Ephemeris

Orbit (dynamics)

Orbit Determination

Precise Point Positioning

Time transfer

10.1186/s43020-022-00072-4

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Citations (6)

Synergetic pyrolysis mechanism of typical organic components of sewage sludge in the presence of CaO: Lipids, proteins, and polysaccharides

Fuel (2024)

Changkai Wang Xiaoxia Yang Butera Hassan Chao Yu Huan He

Sewage sludge

10.1016/j.fuel.2024.133213

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Citations (0)

Real-Time Precise Point Positioning Method Considering Broadcast Ephemeris Discontinuities

NAVIGATION Journal of the Institute of Navigation (2024)

Q.H. Cheng Junping Chen Yize Zhang Chao Yu

Abstract

With advancements in the broadcast ephemeris accuracy of global navigation satellite systems (GNSSs), precise point positioning based on broadcast ephemeris (BE-PPP) is gradually showing promising prospects. However, the periodic updates of GNSS ephemeris result in discontinuities in the satellite orbit and clock offset during handovers. These discontinuities can significantly impact positioning accuracy. In this study, we calculate the combined ephemeris discontinuities, which indicate a linear combination of satellite radial orbit and clock discontinuities. We then compensate for the combined ephemeris discontinuities in the subsequent satellite clocks prior to positioning. For BeiDou Navigation Satellite System 3 (BDS-3) and the Global Positioning System (GPS), the three-dimensional (3D) position accuracy in kinematic mode is improved by 30–50 cm, reaching 33.9 cm. For GPS/Galileo/BDS-3 triple-constellation kinematic solutions, the accuracy reaches 23.2 cm. In static mode, the 3D position accuracy is 14.6 cm for BDS-3-only positioning and 15.1 cm for GPS. For GPS/Galileo/BDS-3 triple-constellation static BE-PPP solutions, the 3D position accuracy improves to 8 cm.

Ephemeris

Classification of discontinuities

Precise Point Positioning

10.33012/navi.643

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Citations (1)

Effects of microfracture parameters on adaptive pumping in fractured porous media: Pore-scale simulation

Energy (2022)

Fachun Liang Zhennan He Jia Meng Jingwen Zhao Chao Yu

Tortuosity

10.1016/j.energy.2022.125950

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Citations (6)

Effect of Slurry Concentration on the Ceramic Ball Grinding Characteristics of Magnetite

Minerals (2022)

Chengfang Yuan Caibin Wu Xin Fang Ningning Liao Jiaqi Tong

Ceramic grinding, which in this paper is defined as a method of using ceramic materials as grinding media, is favored by many processing plants as an emerging high-efficiency and energy-saving grinding method. This paper investigates the effect of slurry mass concentration on the grinding characteristics of magnetite by taking the feed of the secondary ball mill for processing magnetite as the research object. The study results show that the slurry mass concentration significantly affects the ceramic ball grinding characteristics of magnetite, especially for coarse particles. When the grinding concentration is higher than 50%, the breakage rate of magnetite plummets to 1/3 of the value at low mass concentrations. The standard deviation of the breakage rate relative to the concentration gradually decreases as the feed size falls, indicating that the coarser the feed size, the more sensitive the ceramic ball grinding is to the concentration, and thus industrial secondary ceramic ball mills need to avoid grinding under high-quality concentrations. The change in the consistency parameter of distribution function and zero-order output characteristics signals a radical variation in the grinding characteristics of magnetite using the ceramic ball grinding method compared to conventional grinding. Because the ceramic ball grinding method can greatly reduce energy consumption while lowering the chance of overgrinding, this grinding method deserves more attention as the world works to reach carbon neutrality and emissions peak.

Breakage

Ball (mathematics)

10.3390/min12121569

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Citations (9)

Analysis of Extreme Rain and Snow Weather Dynamic and Water Vapor Conditions in Northeast China from 17 to 19 November 2020

Atmosphere (2022)

Chao Yu Hengde Zhang Yu Gong Ning Hu Tao Chen

Based on hourly precipitation data from 2413 national ground observation stations in China and ERA5 (0.25° × 0.25°), this study analyzes the characteristics and causes of extreme rainfall and snow in northeast China from 17–19 November 2020. The results show that extreme precipitation is mainly attributed to the abnormally strong large-scale low vortex and ground cyclone. The significant high-level and low-level coupling in areas with strong rain and snow is conducive to the continuous upward motion, which provides favorable dynamic conditions for the generation and development of extreme precipitation. The frontogenesis effect below the 850 hPa level is obvious, and the extreme precipitation period corresponds to the meeting of the north and south front areas. The symmetrical unstable atmosphere of 925 hPa~700 hPa is forced by the frontogenesis, which strengthens the oblique rising of the low layer and increases the instability, leading to the strengthened development of precipitation. For heavy rainfall and snow in early winter in China, water vapor transport is crucial. The extremely strong low-level jet also provides extremely strong water vapor conditions for the occurrence of heavy rain and snow. The analysis of the extreme rain and snow characteristics and formation mechanism of this weather process can deepen the understanding of extreme weather processes, and provide a useful reference for the research and prediction of extreme precipitation processes.

Frontogenesis

Extreme Weather

10.3390/atmos13081213

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Citations (3)

Pyrolytic mechanisms of typical organic components of sewage sludge in the presence of CaO: Polysaccharides, proteins, and lipids

The Science of The Total Environment (2023)

Xiaoxia Yang Chao Yu Butera Hassan Lun Zhang Changkai Wang

Pyrolytic carbon

Sewage sludge

10.1016/j.scitotenv.2023.166020

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